ETHE1 is a [unreadable]-lactamase fold containing protein that belongs to the GLX2 family of proteins. ETHE1 proteins are found in almost all forms of life including animals, plants, fungi, eubacteria and archaebacteria. Mutations in human ETHE1 were recently shown to be responsible for Ethylmalonic Encephalopathy (EE), a disease resulting in complex metabolic changes that affect the brain, gastrointestinal tract, and peripheral vessels. Experiments in our laboratory have shown that ETHE1 is also an essential gene in plants; mutations in Arabidopsis ETHE1 (AtETHE1) result in embryo lethality. Surprisingly, even though ETHE1 genes are found throughout nature, and are essential for the survival of higher organisms, very little is known about their biochemical/physiological roles, how they function, or the chemical reaction catalyzed by the protein in any organism. [unreadable] [unreadable] As part of studies designed to determine the biochemical role of ETHE1 we have isolated and characterized plants containing AtETHE1 mutations and generated plants that over- and under-express AtETHE1. We have also purified recombinant AtETHE1 and performed a series of biochemical and structural studies to better understand structure/function relationships in this important family of enzymes. In this proposal we will use plants/cell cultures that allow the controlled over- and under-expression of AtETHE1 to investigate how changes in ETHE1 activity affect the metabolic profiles of plants. Based on metabolic alterations associated with EE patients, and our preliminary data in plants we hypothesize that ETHE1 may play a role in propionate metabolism. We will test this hypothesis by comparing the profiles of a number of metabolic intermediates, including short chain acylglycines and organic acids, in plants that either overexpress or lack AtETHE1. Detailed biochemical and structural studies will also be conducted on purified AtETHE and human ETHE1 to directly test potential substrates and ultimately better understand structure/function relationships in the enzymes. [unreadable] [unreadable] [unreadable]